1. Field of the Application
The present application relates in general to propulsion systems for aircraft which are operable in at least a helicopter mode of flight. The present application has a particular applicability in the field of tilt rotor aircraft which are operable in either an airplane mode of flight or a helicopter mode of flight.
2. Description of Related Art
The control systems for helicopters and tilt rotor aircraft are complex electrical and/or mechanical systems. The control systems respond to the pilot's input, but also must accommodate forces acting upon rotor assemblies which are generally outside the control of the pilot. Mechanical control systems typically include a swashplate arrangement which consists of a stationary portion and a rotating portion. Typically, the lower, stationary portion is fixed in position and will not rotate, but has the ability to move up and down and/or tilt in any given direction. This is commonly referred to as the “stationary” or “nonrotating” plate. Pilot inputs alter the vertical position of the stationary plate through the collective control and the tilt of the stationary plate through the cyclic control. The rotating portion of the swashplate arrangement is free to rotate. Of course, pilot inputs to the nonrotating portion are passed through to the rotating portion of the control systems.
The rotating portion is typically connected mechanically to each individual rotor blade. For example, in one type of control system, pitch links are connected to pitch horns which are carried by the rotor blade, thus allowing the rotating plate to alter the blade angle of each rotor blade. However, it is necessary to include in control systems a subsystem which reduces the degree of flapping as much as possible. In the prior art, there are two basic approaches: one is to utilize a delta-3 hinge; the other is to utilize offset pitch horns.
In tilt rotor aircraft, it is especially important to counteract the detrimental effects of flapping, especially because the aircraft is capable of very high speed travel, particularly in the airplane mode of flight. In some scenarios, the excessive flapping and/or other forces exerted by the rotary blades can cause an adverse force on the wing, which could result in failure.
Although great strides have been made in the field of controlling forces of a rotary system, many shortcomings remain.
While the system and method of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the application to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the process of the present application as defined by the appended claims.